The present invention encompasses methods for saponifying organic acid esters, including fatty acid glyceride esters. More specifically, organic acid esters are saponified with an alkali metal hydroxide in a liquid reaction medium comprising a substantially water-free alkyl nitrile to provide unsolvated alkali metal salts of the organic acids. When fatty acid esters are used in the process, dry alkali metal soaps are secured.
The preparation of alkali metal salts of organic acids by saponifying the corresponding organic acid esters, as in traditional soap making processes, is typically carried out using an alkali metal hydroxide base, the organic acid ester, and water as the reaction medium. Heretofore, such reactions have been energy intensive for at least two reasons. First, heat energy is required to initiate and sustain the saponification of the organic acid ester by the aqueous solution of the alkali metal hydroxide. Second, the organic acid salts are strongly solvated by the water from the aqueous reaction medium. Accordingly, some of the water must be removed to recover the organic acid salts, and heat energy is needed for this solvent removal step.
By the present invention, it has been discovered that substantially water-free alkyl nitriles provide a reaction medium wherein organic acid esters can be saponified with alkali metal hydroxides to provide the alkali metal salts of organic acids which precipitate from the reaction medium in an unsolvated form. Accordingly, solvent removal in the present process is not as energy intensive as in the aqueous process. Moreover, the present process is exothermic and, once initiated, proceeds essentially to completion without external heating. Soap making processes carried out in the manner of the present invention using fatty glycerides as the organic acid ester provide substantially dry, unsolvated soap powder in an extremely short period of time in exceptionally high yields.